Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population size has not been quantified, but the species is described as uncommon to fairly common, albeit local (Stotz et al. 1996, Brewer 2020). Based on observed population densities of congeners (H. hypoxanthus and H. ochcraceiceps in Peru: 9-15 mature individuals/km2; Santini et al. 2018), and assuming that only 10% of the mapped range is occupied to account for this species's localised occurrence, the population may number c.55,000-93,000 mature individuals. To account for uncertainty the population size is here placed in the band 50,000-99,999 mature individuals, but an accurate quantification of the population size is required.
Based on observational records (per eBird 2021) the species likely functions as several subpopulations.
Due to its preference for secondary growth, forest edges and clearings, the species is unlikely to be threatened by habitat degradation and loss. Throughout its range, tree cover is lost at a rate of 4% over ten years (Global Forest Watch 2021, using Hansen et al.  data and methods disclosed therein). In the absence of evidence for any declines or substantial threats, the species is tentatively assessed as stable.
This species occurs on the eastern slope of the Andes in Ecuador, from Sucumbíos in the north south to Zamora-Chinchipe, and in Peru from Cajamarca and Amazonas to northern Junín.
The species inhabits forest edge, overgrown clearings and secondary growth at elevations of 600-1,700 m (Brewer 2020). It is mostly observed alone or in pairs, and occasionally in mixed-species flocks (Brewer 2020). The species is very inconspicuous, and not much is known about its ecology and biology.
The species is threatened by the conversion of its habitat for agricultural purposes, but due to its tolerance of secondary and open growth it is currently not considered at risk.
Conservation Actions Underway
The species occurs in several protected areas throughout its range.
Conservation Actions Proposed
Quantify the population size. Research the species's ecology and biology. Monitor the population trend.
12cm, 11-13g. Entirely dull yellow olive vireo with a stout pinksih bill and white iris. Brightest yellow on forehead, belly and throat. Sexes similar. Similar spp. Sometimes considered conspecific with Scrub Greenlet Hylophilus flavipes and the two are very alike. H. flavipes may be darker on forecrown, and paler greyish white on the chin and throat. Voice Distinctive loud "swee-swee-swee" with 10-12 notes repeated. H. flavipes either has a disyllabic note, eg "turee-turee-turee" repeated 4-20 times, or a more slurred, slower double note in Central America.
Text account compilers
Butchart, S., Ekstrom, J. & Symes, A.
BirdLife International (2022) Species factsheet: Hylophilus olivaceus. Downloaded from http://www.birdlife.org on 07/10/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 07/10/2022.